Gas turbine power generation equipment used as e.g. privately-owned electric power generation facilities includes a compressor which compresses air; a combustor which mixes the air compressed by the compressor with fuel for combustion; a turbine which is rotationally driven by combustion gas from the combustor; and a generator which converts the rotational power of the turbine into electric energy. For example, the impeller of the compressor, the impeller of the turbine, and the rotor of the generator are connected to the same rotating shaft. For example, an oil-lubricated type bearing may be adopted as a bearing that rotatably carries the rotating shaft. In such a case, since the bearings cannot be provided at a high-temperature portion (e.g., the compressor and the turbine) where lubricating oil evaporates, they are disposed on both axial sides of the rotor of the generator. Thus, the rotating shaft will rotate at high speeds in an overhang state where the impeller of the compressor and the impeller of the turbine are disposed externally of the bearings. The inherent vibration characteristic of the rotating shaft has to pass through the characteristic frequency of bending vibration mode. The viscosity of lubricating oil increases a power loss of the bearing and further increases the power of a pump which feeds lubricating oil. This increases power consumption for auxiliaries, lowering power generation efficiency.
To deal with this, the following structure is disclosed for example (see e.g. patent document 1). O-rings are fitted into respective O-ring grooves formed in a stationary portion opposed to the outer circumferential portions of a bearing to elastically support the bearing, and an annular clearance is formed between the O-ring grooves. Lubricating oil is filled in the annular clearance to function as a squeeze film. Thus, the damping function of the squeeze film and the spring function of the O-rings damp the vibration of a shaft. In addition, this conventional art adopts a water-lubricated type bearing to reduce the power loss thereof, thereby improving power generation efficiency.    Patent Document 1: JP-A-2004-336917 (see FIG. 5)